Dyspamet

Action

Competitively inhibits histamine action at histamine₂-receptor sites of gastric parietal cells, thereby inhibiting gastric acid secretion

Availability

Oral liquid: 200 mg/5 ml, 300 mg/5 ml

Tablets: 200 mg, 300 mg, 400 mg, 600 mg, 800 mg

Indications and dosages

➣ Active duodenal ulcer (short-term therapy)

Adults and children older than age 16: 800 mg P.O. at bedtime, or 300 mg P.O. q.i.d. with meals and at bedtime, or 400 mg P.O. b.i.d. Maintenance dosage is 400 mg P.O. at bedtime.

➣ Active benign gastric ulcer (short-term therapy)

Adults and children older than age 16: 800 mg P.O. at bedtime or 300 mg P.O. q.i.d. with meals and at bedtime

➣ Gastric hypersecretory conditions (such as Zollinger-Ellison syndrome); intractable ulcers

Adults and children older than age 16: 300 mg P.O. q.i.d. with meals and at bedtime

➣ Erosive gastroesophageal reflux disease

Adults and children older than age 16: 1,600 mg P.O. daily in divided doses (800 mg b.i.d. or 400 mg q.i.d.) for 12 weeks

➣ Heartburn; acid indigestion

Adults and children older than age 16: 200 mg (two tablets of over-the-counter product only) P.O. up to b.i.d. Give maximum dosage no longer than 2 weeks continuously, unless directed by prescriber.

Dosage adjustment

• Renal impairment

Off-label uses

• Acetaminophen overdose

• Adjunctive therapy in burns

• Barrett's esophagus

• Renal cancer

• Anaphylaxis

Contraindications

• Hypersensitivity to drug

• Alcohol intolerance

Precautions

Use cautiously in:

• renal impairment

• elderly patients

• pregnant or breastfeeding patients.

Administration

• Give with meals.

Adverse reactions

CNS: confusion, dizziness, drowsiness, hallucinations, agitation, psychosis, depression, anxiety, headache

GI: diarrhea

GU: reversible erectile dysfunction, gynecomastia

Interactions

Drug-drug. Calcium channel blockers, carbamazepine, chloroquine, lidocaine, metformin, metronidazole, moricizine, pentoxifylline, phenytoin, propafenone, quinidine, quinine, some benzodiazepines, some beta-adrenergic blockers (chlordiazepoxide, diazepam, midazolam), sulfonylureas, tacrine, theophylline, triamterene, tricyclic antidepressants, valproic acid, warfarin: decreased metabolism of these drugs, possible toxicity

Drug-diagnostic tests. Creatinine, transaminases: increased levels

Parathyroid hormone: decreased level Skin tests using allergenic extracts: false-negative results (drug should be discontinued 24 hours before testing)

Drug-food. Caffeine-containing foods and beverages (such as coffee, chocolate): increased cimetidine blood level, increased risk of toxicity

Drug-herbs. Pennyroyal: change in formation rate of herb's toxic metabolite

Yerba maté: decreased yerba maté clearance, possible toxicity

Drug-behaviors. Alcohol use: increased blood alcohol level

Smoking: reversed cimetidine effects

Patient monitoring

• Monitor creatinine levels in patients with renal insufficiency or failure.

• Assess elderly or chronically ill patients for confusion (which usually resolves once drug therapy ends).

Patient teaching

• Inform patient with gastric ulcer that ulcer may take up to 2 months to heal. Advise him not to discontinue therapy, even if he feels better, without first consulting prescriber. Ulcer may recur if therapy ends too soon.

• Advise patient not to take over-the-counter cimetidine for more than 2 weeks continuously, except with prescriber's advice and supervision.

• As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs, tests, foods, herbs, and behaviors mentioned above.